This invention relates to anaerobically-curing compositions and to methods of employing the same.
Two-part, anaerobically-curing compositions are often desirable for many bonding operations such as the situation in which only inactive substrates (e.g., inactive metal substrates such as zinc and cadmium and nonmetallic substrates such as plastic, glass and wood) are involved in the bonding operation. In order to obtain suitable shelf-lives in one-part, anaerobically-curing compositions, such compositions commonly contain polymerization inhibitors as well as lesser amounts of polymerization initiators as compared to two-part compositions. This may result in compromised rates of cure which are particularly evident when the compositions are employed on inactive substrates.
Two-part, anaerobically-curing compositions containing peroxy initiators are well-known in the art. However, those compositions suffer from the disadvantage that in their manufacture one encounters the possibility of explosion when handling large amounts of the peroxy compounds. Furthermore, unfortunately peroxy compounds typically decompose with time, thereby resulting in a steadily decreasing ability of such compounds to initiate polymerization of the compositions containing them.
U.S. Pat. No. 3,658,624 (Lees) describes two-part anaerobically-curing compositions which exhibit suitable cure-rates on inactive surfaces. However, saccharin (o-benzoic sulfimide), which is described therein as a preferred accelerator (i.e., initiator) moiety, is rather insoluble in polymerizable acrylate or methacrylate monomers and therefore renders manufacture of these compositions inconvenient.